(P18-002-24) Characterizing the Changes in Cholesterol Ester Lipid Species During Periods of Inactivity in Middle-Aged and Older Adults

Objectives: Aging adults are at increased risk for injury and illness resulting in extended periods of physical inactivity or hospitalization. Prolonged periods of physical inactivity/bed rest are associated with a lipoprotein profile that contribute to onset of cardiometabolic diseases. Little is known about the changes in specific molecular lipid species of lipoprotein particles associated with the altered lipoprotein profile. The objective of this study was to investigate changes in cholesterol ester (CE) molecular species in middle-aged and older adults during periods of inactivity.

Methods: Older (67.8 ± 1.1 y; n=10; 7 days of bed rest) and middle-aged (52.1 ± 1.0 y; n=9; 14 days of bed rest) adults underwent a rigorous bed rest protocol at the Clinical Research Center at the University of Texas Medical Branch. Meals contained a fixed macronutrient composition (55% carbohydrate, 29% fat, and 16% protein) and caloric intake was adjusted to meet specific energy requirements using the Harris-Benedict equation. Fasting plasma samples were drawn at baseline,7 days of bed rest and 7 days following an inpatient rehabilitation period. CE were extracted from plasma and analyzed by liquid chromatography (LC) tandem mass spectrometry (MS/MS) using C30 reverse phase technology to separate molecular species of CE by their acyl carbon chain lengths and degrees of unsaturation.

Results: The CE 18:2 and CE 20:4 species were the most abundant in both middle-aged and older adults at baseline. None of the CE molecular species showed statistically significant changes in the middle-aged participants after 7 days of bed rest. However, in the older participants 5 CE lipid species were significantly decreased following 7 days of bed rest and 12 CE lipid species were significantly decreased following 7 days of rehabilitation. The decreased CE varied in acyl carbon chain lengths from 16 to 24 and degrees of unsaturation from 0 to 4.

Conclusions: Older adults are more susceptible to changes in CE lipid species. Further investigation is warranted to determine the biological effects of altered CE content and associated impacts on cardiometabolic health.

Funding Sources: National Space Biomedical Research Institute (NNJ08ZSA002N) and from the National Institutes of Health (R01NR012973) awarded to DPJ who supervised EJA-L. Cancer Prevention and Research Institute of Texas awarded to WKR (RP 190682).